Optical recording medium and a method for reproducing information recorded from same

Abstract

The optical recording medium includes a first layer which is in a state that includes different phases having different optical constants and in which information has been recorded. The second layer is capable of changing states, which states include different phases and different optical constants. There is also provided a method of reproducing information recorded on an optical recording medium which includes a first layer having different phases and different optical constants and a second layer capable of changing states, which states include different phases and different optical constants. The method employs irradiating the second layer with a laser beam, and reproducing information recorded on the first layer from an area corresponding to an area of the second layer where the optical constants change due to laser irradiation.

What is claimed is: 
     
       1. A re-writable type optical recording medium comprising: a reproduction auxilary layer including a first phase change material reversible between a crystalline state and an amorphous state, the states having different optical constants, wherein the reproduction auxilary layer is in a first state at room temperature and only a selected portion of the reproduction auxilary layer changes from the first state to a second state while the selected portion is being irradiated by a laser beam during reproduction,   a recording layer including a second phase change material different from the first phase change material, located below the reproduction auxilary layer, having a plurality of portions capable of reversibly changing between an amorphous state and a crystalline state during a recording operation and remaining unchanged during reproduction, wherein the amorphous state and the crystalline state have different optical constants representing information recorded thereon;   wherein the optical recording medium has approximately the same reflectance from areas of the reproduction auxilary layer in the first state so as to form a mask area during reproduction, and the optical recording medium has a different reflectance depending upon the optical constant of the recording layer portion under the selected portion of the reproduction auxilary layer in the second state.   
     
     
       2. The optical recording medium of according to claim 1, wherein the recording layer has a thickness of about 50 to about 300 angstrom. 
     
     
       3. A method of reproducing information recorded on a re-writable type optical recording medium including a recording layer for recording and storing information, comprised of a phase change material having a plurality of portions capable of reversibly changing during a recording operation between an amorphous state and a crystalline state to represent information recorded thereon, and a reproduction auxilary layer comprised of a phase change material different from the recording layer capable of changing during reproduction between an amorphous state and a crystalline state having different optical constants, said method comprising the steps of: irradiating the reproduction auxilary layer with a laser beam to change a selected portion of the reproduction auxilary layer from a room temperature state to an irradiated state;   reproducing information recorded on the recording layer from an area under the selected portion of the reproduction auxilary layer, the optical constant of which changes due to laser irradiation;   wherein the selected portion of the reproduction auxilary layer temporarily changes from the room temperature state to the irradiated state at a temperature higher than its melting point while being irradiated by the laser beam during reproduction to allow detection of the information recorded on the recording layer beneath the selected portion, and the recording layer remains unchanged during reproduction and is reversibly changeable during recording when irradiated at a temperature higher than the melting point for the reproduction auxilary layer.   
     
     
       4. A re-writable type optical recording medium comprising: a recording layer including a phase change material having a plurality of portions capable of reversibly changing between an amorphous state and a crystalline state for storing data, wherein the amorphous state and crystalline state have different optical constants representing information recorded thereon; and   a reproduction auxilary layer including a phase change material different from the recording layer for retrieving data including a portion that changes between a crystallized state and an amorphous state during retrieval of data from the recording layer as a laser beam is applied to the portion,   wherein during data retrieval a selected portion of the material in the reproduction auxilary layer changes from a first to a second state upon being irradiated by a laser beam while the recording layer remains unchanged, and the material remaining in the first state in the reproduction auxilary layer forms a mask area during data retrieval, allowing detection of the information recorded on the recording layer under the selected portion of the reproduction auxilary layer in the second state.   
     
     
       5. The recording medium of claim 4 wherein the first state of the material in the reproduction auxilary layer is the crystalline state, and the second state of the material in the reproduction auxilary layer is the amorphous state. 
     
     
       6. The recording medium of claim 4 wherein the reproduction auxilary layer material is in the amorphous state at room temperature and a selected portion changes to the crystalline state upon being irradiated by a laser beam. 
     
     
       7. The recording medium of claim 6 wherein the laser beam is multiple-reflected on an interface between the recording layer and the reproduction auxilary layer and produces a reflected light serving as an information producing signal or servo signal. 
     
     
       8. The recording medium of claim 5 wherein the laser beam is multiple-reflected on an interface between the recording layer and the reproduction auxilary layer producing a reflected light serving as an information producing signal or servo signal. 
     
     
       9. The recording medium of claim 7 wherein the reflected light has multiple components each having a different optical constant. 
     
     
       10. The recording medium of claim 8 wherein the reflected light has multiple components each having a different optical constant.